DC to DC charger

StirCrazy wrote:

Reisender wrote:
I’m not sure what the source is here. Is it the trucks 12 volt system you want to use to charge the truck campers battery? Why would you need a DC to DC converter for that. That is what the trucks charge line is for on the 7 pin. What am I missing?

We use a DC to DC converter but it is from one static battery bank to another. So no alternator etc.

the 7 pin wire is small, lots of voltage drop. so if your altanator is putting out 13.5V, just to pick a number, by the time it is down at your rv batteries it could be in the 12's, also unless you buy a battery isolater the rv can suck down the truck batteries if you leave it plugged in. I believe newer vehicles may come with that but the wires are still to small.

a dc to dc charger mounts as close to the battery as you can, and you run a new wire, or use your 7 pin, directly from the truck battery to the DC to DC. the charger then turns what ever it is getting into a proper voltage for your batteries. as a bonus it also isolates your truck batteries from the rv batteries so you cannot drain your truck down.

if you use the 7 pin charge line to feed it the inlett amps will be up to 50% higher than the ouput amps, the reason to run a larger wire on a plug is to lower that difference by making less voltage drop on the feed.

so you can also set the charging profiles on the dc to dc charger so if you have deep cycle batteries it will get the best charge as aposed to what ever the starting batteries in the truck get. same goes for gel and Li.

I am installing on in my camper in the spring, this will let me have a emergency source of power for charging if I hit a ton of dark days when I am lait fall/early winter camping. my solar handles everything but last year I saw three days of rain and dark and I was hitting the 50% mark on y deep cycle from running the furnace all the time. I have a 10 day cussion now with the LiFePO4 cell I built but, with the dc tyo dc, in 1.5 hours I can recover 24 hours power use if I need to.

Thanks for the explanation. That all makes sense. I didn’t think it would be a problem with the drop from the alternator but yah. I get it.

We use ours very rarely. When we are dry camping we have a little 2000 watt propane generator we use for keeping the battery up on our little trailer if the solar conditions are bad. (Meaning shady sites etc). But we have stayed at a no generator campground a couple times. We plugged into the 12 volt receptacle in the trunk of the Tesla which kicks out 13.6 volts and then set the DC to DC converter to 14.4 volts to trickle charge the trailer battery for half a day. Got us thru the last couple of days of a camping trip. Handy devices.

Thanks again for the explanation.